Illegal gold mining is posing a threat to Corcovado National Park, home to Costa Rica's most biodiverse forest, media reports said.
The park, located in the Central American nation's southern Pacific region, is home to 3 percent of the world's species.
An investigation conducted by the La Nacion newspaper found that more than 250 people are illegally mining for gold on the banks of the rivers that flow through the 45,700-hectare (112,839-acre) national park.
Miners dig tunnels that can be up to 40 meters (131 feet) long and destroy mountainsides, a practice known as "terracing," the newspaper said.
The miners are destroying one of the world's most biologically diverse places, La Nacion said.
Corcovado is home to 3 percent of the world's species and 50 percent of the species in Costa Rica, Environment and Energy Ministry officials said. EFE